Pulse wave velocity (PWV) is a measure of arterial stiffness or vessel compliance. PWV is a strong indicator of atherosclerosis and vessel stiffness, as well as cardiovascular events and all-cause mortality. PWV estimation may involve measuring the arrival of blood at several points along a vessel, and calculating velocity using these time points and length of the vessel. Traditionally, pulse wave velocity is measured using ultrasound or catheterization to determine pulse pressure. Both of these methods have significant drawbacks. For example, catheterization is highly invasive, while ultrasound distance measurements can be highly inaccurate, resulting in error of as much as 30%.
More recently, phase contrast magnetic resonance imaging (MRI) with multiple acquisition planes has been used to non-invasively measure PWV. A variety of two-dimensional (2D) phase contrast MRI techniques for PWV extraction have been established. While these methods have shown reasonable agreement with literature values, they do have pronounced limitations. For example, existing models for calculation of PWV, such as time-to-foot (TTF) analysis and cross correlation of the flow waveforms, suffer from high variability. Some studies have explored a more comprehensive approach to PWV analysis: plane fitting of flow waveform upslope regions. However, such plane fitting may systematically underestimate PWV, because the gradient of the blood velocity/flow upslope varies along the vessel. Therefore, analysis of this data and reliable calculation of PWV has previously remained challenging.